Surface mining is commonly employed to extract valuable minerals and ores from the earth. In surface mining, the uppermost layers of earth are cut open and removed, or "stripped," in order to expose underlying seams of valuable minerals such as coal or the like. After the seams are mined, the land must then be returned to productive use, or "reclaimed."
Post-mining land reclamation generally involves: (1) replacing the removed minerals and subsurface rock with the spoil from the excavation; (2) grading this spoil; and (3) redepositing earth, or more specifically, soil, over this graded spoil. Vegetation is then replanted in the uppermost layer of soil to restore the land to a useful state.
It is well-known that one of the most important factors in mining site reclamation is to minimize damaging erosion and related adverse long-term environmental impacts of mining operations. In order to achieve the desirable goal of re-establishing productive use of the reclaimed land, it is necessary for the surface soil to support vegetation. One problem associated with the ability of the reclaimed land to support vegetation is the degree of compaction inherent in the replacement soil, which is often created by the reclamation operation itself.
One factor that significantly augments the degree of soil compaction is the weight of the earthmoving equipment used to replace and regrade the soil. As can be appreciated, such heavy equipment exerts a large surface pressure, thereby increasing soil compaction and density. These increases generally produce undesirable changes in the physical properties of the soil, which have seriously detrimental effects on water permeability and plant root growth. This translates directly into poor plant yields and plant stand establishment, which promotes erosion and associated environmental problems. Further, in severe cases, the incidence of dangerous mud or rock slides may result and this often causes related flooding problems.
Previously, others have proposed a variety of solutions to alleviate the problem of soil compaction created during such reclamation operations. One proposal involves the use of a large conveyor system to transport decompacted soil onto previously graded spoil, thereby providing a decompacted rooting layer for planting. Although this reduces the surface traffic caused by machinery and, thus, compaction, such a conveyor system is prohibitively expensive to install, maintain and operate.
Others have proposed the use of different methods of subsoil agitation. In one such method, "rippers" are provided which extend downwardly from the rear of a bulldozer into the soil. After the soil is graded by heavy machinery (which compacts the soil), a bulldozer having these rippers is driven over the compacted soil to agitate and decompact the same. Although such subsoil agitation reduces compaction temporarily, various studies show that subsoiling practices do not return the ability of the land to support vegetation back to the pre-mined state. Additionally, these studies demonstrate that the effects of such subsoiling operations are not permanent, generally lasting less than two years.
Thus, a need is identified for an improved apparatus that transforms compacted soil created during land reclamation operations to a more desirable condition promoting the growth of vegetation. The apparatus is preferably adapted for ready use on pre-existing equipment, thus avoiding expensive retrofitting. Furthermore, the apparatus should be relatively simple and inexpensive to operate and easy to maintain.